Why
dont you try 12 VAC (or less) and a switching regulator at each
location (try using lm2575)
Regards
Javier
Atentamente
Javier A. Fiasche
BLB Ingenieria Aplicada
S.R.L.
T.E. 4381-5884
-----Mensaje original-----
De: Chuck Hackett [mailto:egroupscdh@WhiteTrout.net]
Enviado el: Martes, 01 de Febrero de 2005 03:12 p.m.
Para: AVR-Chat@yahoogroups.com
Asunto: [AVR-Chat] Signal System Power
I'm looking at developing
a signaling application for 1.5" scale ride-onDe: Chuck Hackett [mailto:egroupscdh@WhiteTrout.net]
Enviado el: Martes, 01 de Febrero de 2005 03:12 p.m.
Para: AVR-Chat@yahoogroups.com
Asunto: [AVR-Chat] Signal System Power
railroads (a hobby of mine). It involves a long signal bus (up to a couple of
thousand feet) based on RS-485. I'll also need to run power to operate
ultra-bright LEDs as well as intermittently drive a couple of low voltage, low
power electric motors. The cables will typically be buried along the track.
My design will involve and AVR-based module at locations along the track to
detect trains present on a section of track, signal other modules about track
occupancy, drive local signal (light) heads and possibly low voltage motors to
move throw track switches.
As I see it, I'll have to bury two cables along the track, one for power, and
one for the RS-485 signal bus (either 2-wire or 4-wire with signal ground to
control common-mode voltage differences).
My question at the moment is what is the best way to power the devices along the
network. I don't expect a large current draw at each location (module power
plus several ultra-bright LEDs on at once) and at locations that have small
intermittent motors I could place a small rechargeable battery to take the surge
and trickle charge it from the power bus. Some thoughts:
1) Something like 14-3 house wire carrying 12vdc (since 12vdc is common for
motors, lights, etc.) but I was worried about voltage drop over 1,000's of feet.
Obviously there would be voltage regulators at each module for local logic
power.
2) Same as #1 but use a higher DC voltage (48?) to reduce the current and hence
reduce the voltage drop. How does one get from 48vdc to 3-5 vdc without huge
losses. Cost is a factor here. I realize that I could use a PWM regulator but
are there inexpensive chips for this?
3) Something like 48 VAC. Easier to step down to a reasonable level but I fear
having a transformer, etc. at each module would increase costs too much.
I'm looking to keeping module costs as low as possible and still have a reliable
system.
Comments? Other ideas?
Cheers,
Chuck Hackett
"Good judgment comes from experience, experience comes from bad judgment"
7.5" gauge Union Pacific Northern (4-8-4) 844
http://www.whitetrout.net/Chuck
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